A wireless communication system is a complex network of systems and elements. Typical systems and elements include (1) a radio link to mobile stations (e.g., a cellular telephone or a subscriber equipment used to access the wireless communication system), which is usually provided by at least one and typically several base stations, (2) communication links between the base stations, (3) a controller, typically one or more base station controllers or centralized base station controllers (BSC/CBSC), to control communication between and to manage the operation and interaction of the base stations, (4) a switching system, typically including a mobile switching center (MSC), to perform call processing within the system, and (5) a link to the land line, i.e., the public switch telephone network (PSTN) or the integrated services digital network (ISDN).
A base station subsystem (BSS) or a radio access network (RAN), which typically includes one or more base station controllers and a plurality of base stations, provides all of the radio-related functions. The base station controller provides all the control functions and physical links between the switching system and the base stations. The base station controller is also a high-capacity switch that provides functions such as handover, cell configuration, and control of radio frequency (RF) power levels in the base stations.
The base station handles the radio interface to the mobile station. The base station includes the radio equipment (transceivers, antennas, amplifiers, etc.) needed to service each communication cell in the system. A group of base stations is controlled by a base station controller. Thus, the base station controller operates in conjunction with the base station as part of the base station subsystem to provide the mobile station with real-time voice, data, and multimedia services (e.g., a call).
Typically, the mobile station may detect the presence of multiple base stations that are operable to provide communication services to the mobile station. To assist with synchronization between the mobile station and those base stations, beacon signals are transmitted. In a Third Generation Partnership Project (3GPP) system, for example, the beacon signal is known as a primary synchronization code (PSC) that is transmitted once per slot. The strongest path for the beacon signal is a direct line-of-sight (LOS) path from the base station to the mobile station. However, the signal may reflect off of objects such as buildings and mountains. The mobile station may receive a reflected version of the signal somewhat later than the version via the direct LOS path because the reflected version of the signal may have traveled a longer path to reach to the mobile station, i.e., multi-path signals. Thus, the mobile station performs a searching process to scan through the phase space of the synchronization code looking for valid signals. Based on the energy level of a multi-path signal, the mobile station determines whether to store and report the multi-path signal as a valid signal on a list of possible start points of the synchronization code. Based solely on the energy level of multi-path signals, the mobile station may produce a significant number of results to report.
One aspect of designing a wireless communication system is to reduce the size and consumption power of the mobile station. In particular, one method of improving the availability of resources is to reduce the processing and memory requirements of the mobile station. That is, the loading of the digital signal processor (DSP) and the number of direct memory access (DMA) transfers during a search for multi-path signals may need to be reduced. Therefore, a need exists for a more effective means to process, store, and report results from a search for multi-path signals.